Reflex isolators and branched waveguide networks utilizing the same

ABSTRACT

A reflex isolator using a waveguide having an inlet and an outlet, in which at least one ferromagnetic element having a high specific resistance is provided in the waveguide to shift the maximum points of an electric field in the waveguide when a direct-current magnetic field is applied to the electric field displacement element. Stubs are provided at the shifted maximum points of the electric field to reflect microwaves from the outlet. Two reflex isolators are respectively provided at two branching waveguides in a Y-branch waveguide to form a microwave coupler, in which coupling between the two branching waveguides is effectively suppressed.

v United States atent 1 Suzuki REFLEX ISOLATORS AND BRANCHED WAVEGUIDE NETWORKS UTILIZING THE 21 Appl. No.: 285,636

[52] US. Cl. 333/9, 333/242, 333/98 M [51] Int. Cl. 01p 1/32, HOlp 5/12 [58] Field of Search 333/6, 7, 9, 24.2, 98 M [56] References Cited UNITED STATES PATENTS 8/1958 Miller 333/242 X 11/1965 Thomas et al. 333/242 X OTHER PUBLICATIONS Soohoo, Theory & Application of Ferrites, Prentice-Hall NJ. 1960, P. 218 cited, TK7870S55.

von Aulock et 21., Linear Ferrite Devices for Microwave Applications, Academic Press, N.Y., 1968 TK7803A3, P. 52 cited AU255.

Primary Examiner-Paul L. Gensler Attorney, Agent, or Firm-Robert E. Burns; Emmanuel J. Lobato [57] ABSTRACT A reflex isolator usinga waveguide having an inlet and an outlet, in which at least one ferromagnetic element having a high specific resistance is provided in the waveguide to shift the maximum points of an electric field in the waveguide when a direct-current magnetic field is applied to the electric field displacement element. Stubs are provided at the shifted maximum points of the electric field to reflect microwaves from the outlet. Two reflex isolators are respectively provided at two branching waveguides in a Y-branch waveguide to form a microwave coupler, in which coupling between the two branching waveguides is effectively suppressed.

4 Claims, 22 DrawingFigures Wgb PATENTEU 51974 3.795.875

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our PUT Du m A L O 5 I TRANSMITTER REFLEX ISGLATORS AND BRANCHED WAVEGUIDE NETWORKS UTILIZING THE SAME This invention relates to a reflex isolator using a wave guide.

There have been heretofore proposed in the art, unidirectional wave guides comprising Faraday rotation isolators, field displacement isolators or resonance absorption isolators. However, these unidirectional wave guides also known as unidirectional attenuators are so designed that microwaves transmitted therein are only slightly attenuated in a desired direction while microwaves transmitted therein in the reverse direction are absorbed in a resistor or a ferrite. Accordingly, waves injected in one inlet of the unidirectional waveguide are transmitted while waves injected in the other inlet of the unidirectional wave guide are absorbed. In other words, the conventional unidirectional waveguides do not obtain their characteristics by reflecting microwaves. 1

If respective outputs of two microwave sources are to be applied to a waveguide, filters are inserted at the outputs of the two microwave sources respectively in accordance with conventional techniques for mutually reflecting microwaves from the other of the two microwave sources. However, if the frequencies of the microwaves generated from the two microwave sources are equal to each other or have only a small frequency difference therebetween, the above mentioned insertion of the filters cannot be applied. Moreover, even if the above frequency difference is sufficient to allow the filtering technique the frequency selection characteristics of the filters must be adjusted in response to change of the frequencies of the microwave sources.

An object of this invention is to provide a reflex isolator that provides a low loss transmission path to microwaves injected into the inlet of the isolator and substantially reflects all of the microwaves injected into the outlet of the isolator.

Another object of this invention is to provide a microwave coupler using reflex isolators for coupling a waveguide and at least two waveguides so as to combine microwaves or divide microwaves in a specified wide frequency band irrespective of a frequency difference therebetween.

The principle, construction, and operations of this invention will be understood from the following detailed description taken in conjunction with the accompanying drawings, in which the same parts are designated by the same reference numerals, characters and symbols, and in which:

FIGS. 1A, 1B and 1C are respectively a perspective view, an elevation and a longitudinal section illustrating an embodiment of a reflex isolator of this invention;

FIG. 2 is a fragmentary schematic elevation explanatory of the operation of the embodiment shown in FIGS. 1A, 1B and 1C;

FIGS. 3A and 3B are a perspective view and an elevation illustrating another embodiment of a reflex isolator of this invention;

FIG. 4 is a fragmentary schematic elevation explanatory of the operation of the embodiment shown in FIGS. 3A and 33;

FIGS. 5A and 5B are a perspective view and an elevation illustrating another embodiment of a reflex isolator of this invention;

FIG. 6 is a fragmentary schematic elevation explanatory of the operation of the embodiment shown in FIGS. 5A and 58;

FIGS. 7, 8, 9, 10 and l I are respectively a plan view, a perspective side view, an elevation, a bottom view including a section, and a perspective side view after removing the permanent magnets, of an example of a microwave coupler of this invention;

FIGS. 12 and 13 are connection diagrams each illustrating an application of the microwave coupler of this invention; and

FIGS. l4, 15, 16, 17 and 18 are respectively a plan view, a perspective side view, an elevation, a bottom view including a section, and a perspective side view after removing the permanent magnets, of another example of a microwave coupler of this invention.

With reference to FIGS. 1A, 1B and 1C, an embodiment of this invention comprises a waveguide 1, an inlet 2, an outlet 3 opposed to the inlet 2, a ferromagnetic element 4 having a high specific resistance such as a ferrite or YIG (Yttrium, Iron, Garnet) device, stubs 5 provided for reflecting input waves from the outlet 3, stubs 6 provided for matching with input waves from the inlet 2, and a permanent magnet 7 employed for applying a direct-current magnetic field to the electric-field displacement element 4.

If sizes of the waveguide l and the electric-field displacement element 4, distances between the electricfield displacement element 4 and the walls of the waveguide 1, and the intensity of the direct-current magnetic field are adjusted for the specified frequency band, the maximum point of the electric field of a microwave travelling along the forward transmission direction of the reflex isolator from the inlet 2 to the outlet 3 is kept at a distance from the electric-field displacement element 4 as shown in FIG. 2 while the maximum of the electric field of a microwave travelling along the backward transmission direction of the reflex isolator from the outlet 3 to theinlet 2 coincides with the position of the electric-field displacement element 4.

The length and spacing of the stubs 5 are so adjusted that waves to be reflected in the reflex isolator are reflected by the stubs 5 provided in the electric-field displacement element 4. Moreover, the stubs 6 provided at the maximum point of the electric field of a microwave travelling along the forward direction are adjusted so as to establish matching with the microwave.

' As a result of the above construction, microwaves travelling along the forward direction are transmitted at a low loss while microwave injected in the backward direction can be substantially totally-reflected.

With reference to FIGS. 3A and 3B, another embodiment of this invention comprises a convex waveguide 1, an inlet 2, an outlet 3, electric-field displacement elements 4a and 4b such as ferrite and YIG (Yttrium, Iron, Garnet) devices, stubs 5 provided for reflecting injected waves from the outlet 3, and permanent magnets 7a and 7b provided for applying direct-current magnetic fields to the electric-field displacement elements 4a and 4b. This embodiment is constructed in accordance with a principle of the grooved waveguide, in which a center groove provided at a wide wall of a rectangular waveguide operating in the TE mode causes no effect on the transmission of waves.

In this embodiment, when the direct-current magnetic fields are applied to the electric-field displacement elements 411 and 4b, the maximum point of the electric field of a microwave travelling along a backward direction from the front to the back of a drawing paper is deviated to the left as shown by a solid line in FIG. 4. The channel 8 is deviated to the left from the center of the waveguide so that the microwaves travelling along the backward direction are leaked into the channel 8. Since the maximum point of the electric field of a microwave, travelling along a forward direction towards the viewer of the drawing paper is deviated to the right hand as shown by a dotted line in FIG. 4, the microwave travelling along the forward direction is not leaked into the channel 8. As mentioned above, the microwaves injected in the backward direction are substantially totally-reflected by providing the stubs 5 inthe channel 8.

With reference to FIGS. 5A and 5B, another embodiment of this invention comprises a rectangular waveguide I, an inlet 2, an outlet 3, electric-field displacement elements 4a and 4b such as ferrite or YIG devices, stubs 5 provided for reflecting injected waves from the outlet 3, and permanent magnets 7a and 7b provided for applying direct-current magnetic fields to the electric-field displacement elements 40 and 4b.

In this embodiment, when the direct-current magnetic fields are applied to the ferromagnetic element of high specific resistance 4a and 4b, the maximum point of the electric field of a microwave injected from the inlet 2 is deviated to the left as shown by a solid line in FIG. 6, while the maximum point of the electric field of a microwave injected from the outlet 3 is deviated to the right as shown by a dotted line in FIG. 6. Accordingly, the stubs 5 are provided at a deviated position of the waveguide l, at which the microwave injected from the inlet 2 has a weak intensity while the microwave injected from the outlet 3 has a strong intensity. The stubs 5 are so adjusted that the microwave injected from the inlet 2 is transmitted at the wave guide 1 in a low loss while the microwave injected from the outlet 3 is effectively reflected.

The above mentioned reflex isolators can be applied to form a microwave coupler of this invention, which is employed for combining outputs of two microwave sources at a waveguide and for branching the output of a microwave source into two waveguides. The above combining and branching can be performed irrespective of a frequency difference between respective output frequencies of the two microwave sources, without mutual interference of the respective outputs, and at a low transmission loss.

With reference to FIGS. 7, 8, 9, 10 and 11, an example of the microwave coupler of this invention comprises inlets or outlets P, and P of a Y-branch rectangular waveguide, another inlet or outlet P ferrite plates Fe, and Fe provided at inside walls of the branching part of the Y-branch rectangular waveguide, permanent magnets M, and M employed for applying direct-current magnetic fields to the ferrite plates Fe, and Fe from the outside of the waveguide, and stubs 11 to 29 employed for performing impedance matching. The stubs 11 to 19 are provided on a longitudinal bisector ofa part of the wave guide from the outlet (or inlet) P to the branching part. The stubs 20 to 24 are provided on an array line shifted to the outside from the longitudinal bisector of a branching waveguide including the inlet or outlet P,. The stubs 25 to 29 are provided on an array line shifted to the outside from the longitudinal bisector of a branching waveguide including the inlet or outlet P The above array lines coincide with the maximum positions of microwaves shifted by the function of the ferrite plates Fe, and Fe and the applied direct-current magnetic fields. The spaces of the stubs 11 to 29 are equal to a quarter of the waveguide wavelength of a center frequency of a specified frequency band for obtaining a wideband characteristic.

In case of the combining operations, impedance matching is performed by the stubs 11 to 29 for microwaves, which are injected from the inlets P, and P shifted to the outsides by the ferrite plates Fe, and Fe, and the direct-current magnetic field, and transmitted to the outlet P;,, so that the input waves from the inlets P, and P;, can be transmitted to the outlet P at low losses. In other words, the stubs 11 to 29 are not impedance-matched with microwaves from the inlets P, or P, to the inlets P or P,, so that transmission between the inlets P, and P can be suppressed. A reason for this is that the maximum positions of the electric fields of microwaves travelling to the inlets P, and P, from the branching part of H-plane Y-branch waveguide are shifted to inside walls of the branch waveguides having the ferrite plates Fe, and Fe by the function of the ferrite plates Fe, and Fe and the direct-current magnetic fields. The value of the shift can be desirably varied by the size and form of the ferrite plates Fe, and Fe, and the intensity of the direct-current magnetic field.

The above impedance matching may be performed by dielectric elements, waveguide windows or ridge waveguides.

In case of the branching operations, the polarity of the direct-current magnetic fields is reversed so that the microwave from the inlet P, can be equally divided into two parts and respectively applied to the outlets P, and P at a low loss.

The above mentioned coupler can be constructed by the use of a circular waveguide. Moreover, the ferrite plates Fe, and Fe can be separately provided from the inside walls of the branching waveguide.

With reference to FIG. 12, outputs of a plurality of solid oscillators or amplifiers SS connected to the output ofa signal generator SS can be combined with one another by use of connection waveguides g and couplers y of this invention to obtain the high power output, which cannot be obtained by a single oscillator.

With reference to FIG. 13, outputs of a plurality of transmittors Tx can be combined with one another after passing through isolators IS by connection waveguides g and couplers y of this invention for applying microwaves to antenna ANT. In accordance with the arrangements shown in FIGS. 12 and 13, the necessary power for each oscillator or transmitter can be effectively reduced in comparison with conventional apparatus while cross modulation between combined waves is avoidable.

The above coupler can be modified as shown in FIGS. 14, l5, 16, 17 and 18. Only the parts different from the above coupler shown in FIGS. 7, 8, 9, l0 and 11 are described for simple explanation. Each of the permanent magnets M, and M have two pairs of magnetic poles. Two ferrite plates Fe,,, and Fe are provided at both walls of the branching waveguide including the inlet P, as shown in FIG. 17, while two ferrite plates Fe and Fe are provided at both walls of the branching waveguide including the inlet P A pair of opposed stepped regions or staircases 8T and 8T are provided at opposed walls of the waveguide at the branching part for suppressing generation of higher modes. In this case, the length of each step is equal to a quarter of the waveguide wavelength, while the width W of a most widened part of the branching part is equal to 1.35 times the wavelength of a center frequency of a desired usable frequency band. The heights of the steps are equal to one another. The operations of this modification are similar to the operations of the example shown in FIGS. 7, 8, 9, l0 and 11. Moreover, generation of higher modes can be effectively suppressed by this modification.

As understood from the above explanation, the reflex isolators and the couplers of this invention can be applied to microwave communication facilities, such as setellites, terrestrial stations for satellite communication and surface microwave communication facilities.

What I claim is: v

l. A reflex isolator, comprising:

a waveguide having an inlet and an outlet opposed to the inlet;

at least one ferromagnetic element of high specific resistance longitudinally provided in the waveguide;

means for applying a direct-current magnetic field to said electric-field displacement element for shifting the maximum points of an electric field in said waveguide;

stubs provided in said electric-field displacement element for reflecting microwaves from said outlet; and

stubs provided in said waveguide for matching with the microwaves from said inlet.

2. A reflex isolator, comprising:

a convex waveguide having an inlet, an outlet opposed to said inlet and a longitudinal channel shifted from the center line thereof;

at least one ferromagnetic element of high specific resistance longitudinally provided in the waveguide;

means for applying a direct-current magnetic field to said electric field displacement element for shifting the maximum points of an electric field in said waveguide to the position of the longitudinal projection; and

stubs provided along said longitudinal projection for reflecting microwaves from said outlet while microwaves from the inlet are transmitted at a low loss.

3. A microwave coupler, comprising:

a Y-branch waveguide having a main waveguide and two branching waveguides connected at a junction to the main waveguide;

at least two ferromagnetic elements of high specific resistance provided at the junction;

means for applying direct-current magnetic fields to said two electric-field displacement elements for shifting the maximum points of electric fields in the two branching waveguides; and

stubs provided in the two branching waveguides along the shifted maximum points of the electric fields for reflecting microwaves between the two branching waveguides.

4. A microwave coupler according to claim 3, in

which a pair of opposed stepped regions are provided at opposed walls of the waveguide at the junction to suppress generation of higher modes. 

1. A reflex isolator, comprising: a waveguide having an inlet and an outlet opposed to the inlet; at least one ferromagnetic element of high specific resistance longitudinally provided in the waveguide; means for applying a direct-current magnetic field to said electric-field displacement element for shifting the maximum points of an electric field in said waveguide; stubs provided in said electric-field displacement element for reflecting microwaves from said outlet; and stubs provided in said waveguide for matching with the microwaves from said inlet.
 2. A reflex isolator, comprising: a convex waveguide having an inlet, an outlet opposed to said inlet and a longitudinal channel shifted from the center line thereof; at least one ferromagnetic element of high specific resistance longitudinally provided in the waveguide; means for applying a direct-current magnetic field to said electric field displacement element for shifting the maximum points of an electric field in said waveguide to the position of the longitudinal projection; and stubs provided along said longitudinal projection for reflecting microwaves from said outlet while microwaves from the inlet are transmitted at a low loss.
 3. A microwave coupler, comprising: a Y-branch waveguide having a main waveguide and two branching waveguides connected at a junction to the main waveguide; at least two ferromagnetic elements of high specific resistance provided at the junction; means for applying direct-current magnetic fields to said two electric-field displacement elements for shifting the maximum points of electric fields in the two branching waveguides; and stubs provided in the two branching waveguides along the shifted maximum points of the electric fields for reflecting microwaves between the two branching waveguides.
 4. A microwave coupler according to claim 3, in which a pair of opposed stepped regions are provided at opposed walls of the waveguide at the junction to suppress generation of higher modes. 